Polyoxyalkylene lubricant composition



2,717,242 POLYOXYALKYLENE LUBRICANT COMPOSITION Edward G. Foehr, SanRafael, Califi, assignor to California Research Corporation, SanFrancisco, Calif., a'

corporation of Delaware 7 No Drawing. Application December 5, 1951,

Serial No. 260,113

6 Claims. (Cl. 252-496) The present invention relates to the preparationof novel oleaginous compositions useful as lubricants. Moreparticularly, the invention has to do With the preparation oflubricating oil compositions comprising, as essential ingredients,polymeric material of the polyoxyalkylene type and an organo siliconcompound which is an ester of a silicic acid.

The problem of keeping abreast with the constantly changing andincreasingly exacting lubrication requirements of engines constantlybeing developed, particularly aircraft and automotive, is a major oneconfronting the petroleum industry. For example, continued refinement ofgas turbine engines, such as turbo-jets and turbo-props, depends to agreat extent on the development of lubricants capable of satisfactorilylubricating the moving parts, such as bearings and gears, of theseengines.

While heretofore lubricating oils based on mineral hydrocarbon oils havebeen modified to render them suitable for increasingly exacting uses byimproved refining techniques and by the use of additives, suchlubricating oils suffer from certain inherent disadvantages which limitthe usefulness thereof.

Thus, lubricating oil compositions are constantly being sought whichhave improved viscosity-temperature relationships, that is, a lowviscosity at low temperatures, for example, -65 F. and lower, to permiteasy starting, and high viscosity at high temperatures, up to as high as500' F., to retain lubricity and thus prevent scuffing of metal parts;improved stability against oxidative deterioration in high temperatureoperations; improved volatility characteristics so that at the highertemperature, loss of lubricant through vaporization is minimized;improved antiwear properties when used with highly loaded bearings andgears, and improved anti-corrosion properties.

Accordingly, an object of the invention is to prepare lubricating oilcompositions having improved viscositytemperature characteristics.

Another object of the invention is to prepare lubricating oilcompositions having improved volatility properties at high temperatures.

Still another object of the invention is to prepare lubricating 'oilcompositions having superior anti-wear properties for highly loadedbearings and gears.

Yet another object of the invention is to prepare lubricating oilcompositions having improved resistance toward oxidative deterioration.

These and other objects and advantages of the invention will be apparentfrom the ensuing description of the invention.

Broadly, the invention is predicated on the discovery that a blend ofpolyalkylene glycol polymeric material and soluble therein an ester of asilicic acid in proportions, by volume, of about at least per centofeither component, and the remainder, the other component, has superiorviscosity-temperature properties, good volatility characteristics,unexpected anti-wear properties, and high stability toward oxidation andcorrosion.

The amount in the blend of either component can range 2,717,242 PatentedSept, 6, 1955 ICE . from about one-fourth to four-fold the amount, byvolume, of the other component, that is, 20 to per cent, preferably 40to 60 per cent, by volume, of either component. Often the organo siliconcompound and polyalkylene glycol polymeric material are advantageouslyemployed in equal amounts by volume.

The preferred esters contemplated by the invention are those oforthosilicic acid conforming to the formula wherein R, R1, R2 and R3 arelike or different organic hydrocarbons, or equivalent, groups of 1,preferably at least.3, to about 18 carbon atoms, most advantageously 5to 8 carbon atoms, such as alkyl, ar'yl,alkaryl, arylalkyl, alkoxyalkyl,alicyclic, saturated and unsaturated, for ex ample, methyl, ethyl,propyl, butyl, amyl, hexyl, heptyl, octyl, decyl, butoxyethyl, vinyl,benzyl, xylyl, xenyl, allyl, butenyl, cyclohexyl, phenyl, etc.

In addition, those orthosilicates are preferred in which the carbonatoms in the organic portion of the molecule are of branched chainstructure, such as those derived from secondary and tertiary alcohols orprimary alcohols having alkyl substituents in the 2-position. It hasbeen found that hydrolytic stability is greatest with tertiary carbonstructure and decreases in the order of secondary carbon structure,followed by branched-chain normal and then straight. normal. Likewise,oxidative stability decreases in the order of tertiary, primary, andsecondary carbon structures. Ideally, therefore, the orthosilicateselected will be one in which the. carbon groupings will all be oftertiary carbon structure, and Where this is not permitted, a maximumnumber of tertiary carbons, with the remainder being primary carbonchains.

Specific examples of orthosilicate esters contemplated by the inventionare tetraethyl silicate, tetraisopropyl silicate, tetra (n-butyl)silicate, tetra (2,2-dimethyl propyl) silicate, tetra (2-butyl)silicate, tetra (2-pentyl) silicate, tetra (3-amyl) silicate, tetra(Z-methyl-l-butyl) silicate, tetra (Z-methyI-Z-butyl) silicate, tetra(n-hexyl) silicate, tetra (Z-hexyl) silicate, tetra (4-methyl-2-pentyl)silicate, tetra (Z-ethyl-l-butyl) silicate, tetra (Z-heptyl) silicate,tetra (2-octyl) silicate, tetra (2,4-dimethyl-3-pentyl) silicate, tetra(Z-ethyl-l-hexyl) silicate, tetra (n-decyl) silicate, tetra(l-methoxyl-Z-propyl) silicate, tetra (n-dodecyl) silicate, tetra(n-hexadecyl) silicate, tetra (n-octadecyl) silicate, tetra(l-butoxyl-Z-propyl) silicate, bis (2- butyl) bis (Z-ethyl-l-butyl)silicate, isopropyl-tris (2- pentyl) silicate, bis phenyl-bis(4-methyl-phenyl) silicate, tetra (4-methyl-phenyl) silicate, tetra(4-methyl-phenyl) silicate, tetraphenyl silicate, tetracyclohexylsilicate, tetra (4-vinyl-phenyl) silicate, tetra (Z-butoxyethyl)silicate, tetra (2 methoxyphenyl) silicate, and tetra (2 cyclohexenyl)silicate.

While the esters of orthosilicic acid are preferred in carrying out theinvention, esters of other silicic acids can be employed in accordancewith the invention. These may be represented by the formula OR FOR "I ORROEii0-S i0di-OR a... La. la,

in which n is zero for esters, of disilicic acid or at least 1 for thehigher silicic acids, such as trisilicic acid. In general the R groupsin the aboveformula are similar or dissimilar organic radicals of likedefinition given for the characterization, of the orthosilicates, thepreferred groups being of branched chain structure as already describedin defining the orthosilicates.

The preferred class of polyoxyalkylene polymeric material, the otheressential ingredient of the blend, is that having the polymericstructural configuration dicated, unexpected. Thus the compositions ofthe present invention have wear characteristics which are better (g lthan either ingredient taken alone. A convenient method E() I I ofdetermming this property and the one utilized in ob- 5 taining the dataappearing in the examples, is the well- These materials are P p from thealkylene known Falex wear test, described, for example, in the ides.such s ethylene Oxide, -p py oxide, the Journal of the Institute ofPetroleum, vol. 32, April butylel'le Oxides 2111d higher hOIIlOlOgS, andIIIiXlUTeS 1946. In obtaining the data hereinbelow appearing, thethereof, and the Corresponding alkylene y The following conditions wereobserved: Speed, 300 R. P. M., resulting Products y be p y y y dliols PY- load, 500 lbs; time, 30 minutes; specimens, steel allrylene glycolderivatives in which one or both of the on Steel, h i h f h h ft befor dft th terminal Y Y gTOlIPS have been removed either test was noted, theloss in weight in milligrams indicating ing the polymerization reactionor subsequently thereto, h amount f weal; as by etherification OIesterification, l0 mono- OI Compositions of the present invention mayhave a i r 0r mOHO- I p Combinations wear rate of as low as 3 mg. weightloss; the order of f Such terminal gYOUPS, whereby Certain P P' wear ofa typical high grade mineral oil is around 30 mg. fifties. are impalztedt0 t final Polymeflc mlXtl-lre- The tabulated data appearing belowillustrate the un- Y y of llll-lsflallont Palenl 2,443,664 expected wearsuperiority of the present compositions. t q the P P F Of a y l yP py PThese data were obtained employing the wear test heremeric mixtureaccording to the equation: inabove mentioned. The numerals appearingafter ROH +'n(OCzHs-CHa) R(OC2H3-CH3)11OH Tetra (2-ethylhexyl) silicateand the polyalkylene gly- Monohydric 1,2-pr0pylene Polyoxypropylene mon0col polymeric material, Sec.-butyl methyl polypropylene 1 1 wide hydroxycompound glycol diether (m. w. about 600) indicate amounts of Ashereinabove indicated, the terminal hydroxyl group each in volume percent. The numerals appearing after may be removed or capped byesterification or etherifica- Wear indicate weight loss in milligrams,two tests betion to yield a mono-ether mono-ester or diether polyingperformed for each column.

Tetra (2-ethylhexyl) silicate. 100 80 60 40 0 Sec.butyl methylpolypropylene glycol diether (m.w. about 600) 0 20 40 100 Wear 11.1,9.s3.1,a2 3.5,a9 1.6,0.8 6.3,6.1

propylene glycol, respectively. Indeed, for purposes of the presentinvention, a polyalkylene glycol free of terminal hydroxyl groups, thatis, one having either terminal ester and/or ether groups is preferred.

Polyoxyalkylene polymeric and copolymeric mixtures containing polymerunits having more than two carbon atoms separating oxygen atoms havealso been prepared and described. For example, U. S. Patent No.2,520,733 describes the preparation of polymers and copolymers derivedfrom trimethylene glycol.

The foregoing compounds, as well as additional polymeric materialscontemplated by the invention, are further described in U. S. Patent No.2,491,432. These compounds and materials range in molecular weight fromabout 400 to 2000 and higher. Most advantageously employed in accordancewith the invention are monoethermonoester or diether derivatives ofpolyalkylene glycols having a molecular weight between about 400 and800, preferably between about 400 and 600.

As hereinbefore indicated, the compositions prepared in accordance withthe invention have certain properties, due to the conjoint presence ofthe two essential ingredients of polyalkylene glycol polymer and organosilicon compound which render them suitable for uses having moststringent requirements. To illustrate, it is desirable that a gasturbine lubricant have not to high a viscosity at low temperatures, thatis, not more than 5000-40000 centistokes at F.; not too low a viscosityat the higher temperatures, that is, a minimum of about 3 centistokes at210 F.; a minimum volatility, as measured by flask (Cleveland open cup),not below about 300 F., preferably not below 350375 F.; a maximum pourof below 65 F., and, preferably, below -75 F; a viscosity-temperatureslope between 210 F. and 65 F. not exceeding about 0.75. Otherproperties are oxidative stability and anti-corrosion, good oiliness andability to lubricate under extreme pressure conditions. Also desirableis good response to the addition of one or more additives to modify theproperties of the compositions desirably.

A most important property of the composition prepared in accordance withthe invention istheir good wear characteristics. Indeed, thesuperiorityv of the present compositions in regard to wear is, asvhereinbefore in- The data indicate that whereas the silicate alone gavea weight loss of 11.1 and 9.6 mg. and the polyalkylene glycol polymericmaterial alone gave a weight loss of 6.3 and- 6.1 mg, addition of 20 percent or more of one to the other resulted in a substantial reduction ofweight loss.

The following examples further illustrate. compositions prepared inaccordance with the invention.

Example 1 Polymeric material having a viscosity of 61.2 seconds Saybolt(SSU) at 210 F. and prepared from 1,2-propylene oxide and Z-ethylhexanolwas mixed in equal amounts, by volume, with tetra (Z-ethylhexyl)orthosilicate. Addition of 1% phenyl-a-naphthyl amine and 6%polymethacrylate viscosity index improver resulted in a compositionsuitable for turbo-prop lubrication.

The composition analyzed as follows:

1 Utilizing ASTM Standard Viscosity-Temperature C art E for LiquidPetroleum Products (IQ-341)., the ratio of the linear distance betweenmeasured vlscosities at 10 F. and 210 F. plotted on the ordinate, andthe linear distance between temperatures of 40 13. and 210 F. measuredalong the abscissa.

Example 2 An n-butyl methyl polypropylene glycol diether having amolecular weight of about 500 was mixed with tetra (-2-ethylhexy1)orthosilicate in amounts of 30 and volume per cent, respectively. To theresulting blend there was added, by weight of the finished composition,0.05 per cent mercaptobenzothiazole and 0.1 per cent 1 ,3 ,4thiadiazolyl-2,5-bls(dialkyl dithiocarbamate) The finished composition,suitable as a-lubricant for turbojets and turbo-props, analyzed asfollows; 1

About 80 volume per cent hexa(2-ethyl-1-butoxy) disiloxane was mixedwith about volume per cent of nbutyl methyl polypropylene glycoldiether. The composition analyzed as follows:

An n-butyl methyl diether copolymer of ethylene oxide- 1,2-propyleneoxide, in a mol ratio of ethylene oxide to 75 mol per cent propyleneoxide and having a molecular weight of about 500 was mixed in equalproportions by volume with 4-methyl-2-pentyl silicate. The resultingcomposition, useful as a gas turbine lubricant and bydraulic fluid, hadthe following properties:

Flash, Cleveland open cup, F 350 Fire, "F 390 Viscosity, in centistokes:

At 210 F- 2.15 At 100 F 6.5 At 65 F 2800 Viscosity index 144 Pour point,F below 80 F.

Example 5 About volume per cent of polytrimethylene glycol polymer(molecular weight, about 860) was mixed with about 70 volume percent oftetra (butoxyethyl) orthosilicate. To this mixture was added about 0.5%of phenothiazine and 0.1% of mercaptobenzathiazole. The finishedcomposition was useful as a hydraulic transmission fluid. It analyzed asfollows:

Flash, Cleveland open cup, "F 380 Viscosity, in centistokes:

At 210 F 2.55 At 100 F 7.6 At 30 F 290 Viscosity index 178 Example 6 Auseful composition for the lubrication of sensitive instrumentsrequiring freely moving parts for accuracy, breech mechanisms and thelike was made up by mixing about 10 volume per cent polypropylene glycolhaving a molecular weight of about 630 with about 90 volume per centtetra (A 2-propyl, 2-octyl orthosil icate. The

composition had the following properties:

Flash, "F V 350 Viscosity, in centistokes:

At 210 F 2.1 At F 6.5 At -30 F 300 Viscosity ind 134 Example 7Polypropylene glycol mono isooctyl ether having a molecular weight ofabout 600 was mixed in equal proportions by volume with hexa(Z-methylbutyl) disiloxane.

. The finished composition was useful as a hydraulic transmission fluid,gas compressor lubricant, or turbine oil. It

analyzed as follows:

Flash, Cleveland open cup, F 370 Viscosity, in centistokes:

At 210 F 3.3 At 100 F 11.5 At 30 F 600 Viscosity index 177 As will occurto those skilled in the art, and as has hereinabove been indicated, thecompositions of the present invention are useful as gas turbinelubricants, hydraulic fluids, instrument oils, turbine oils,transmission fluids, ice machine oils, and others. Those oils may beimproved, moreover, by the presence of one or more inhibitors, and asoxidation and corrosion inhibitors, anti- Wear agents, rust inhibitors,foam inhibitors, etc.

Obviously, many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claims.

I claim:

1. A lubricant composition comprising a dialkyl poly- 1,2-propyleneglycol diether having a molecular weight of from about 400 to 800 andwherein the alkyl end groups contain from 1 to 8 carbon atoms, togetherwith an amount of from about one-fourth to about four-fold, in terms ofthe volume of said ether, of a member of the group consisting oftetraalkyl silicate and hexaalkoxy disiloxane wherein said alkyl groupscontain from 5 to 8 carbon atoms each and have a branched-chainstructure.

2. A lubricant composition comprising a dialkyl poly- 1,2-propyleneglycol diether having a molecular weight of from about 400 to 800 andwherein the alkyl end groups contain from 1 to 8 carbon atoms, togetherwith an amount of from about one-fourth to about four-fold, in terms ofthe volume of said ether, of a tetraalkyl silicate wherein said alkylgroups contain from 5 to 8 carbon atoms and have a branched-chainstructure.

3. A lubricant composition comprising a dialkyl poly- 1,2-propyleneglycol diether having a molecular weight of from about 400 to 800 andwherein the alkyl end groups contain from 1 to 8 carbon atoms, togetherwith an amount offrom about one-fourth to about four-fold, in terms ofthe volume of said ether, of a hexaalkoxy disiloxane wherein said alkoxygroups contain from 5 to 8 carbon atoms and have a branched-chainstructure.

4. A lubricant composition comprising a sec.-butyl methyl polypropyleneglycol diether having a molecular weight of from about 400 to 800 andfrom about onefourth to about four-fold, in terms of the volume of saidether, of tetra(2-ethyl hexyl) silicate.

5. A lubricant composition comprising a di(2-ethyl hexyl) polypropyleneglycol diether having a molecular weight of from about 400 to 800 andfrom about onefourth to about four-fold, in terms of the volume of saidether, of tetra(2-methyl hexyl) silicate.

2,7175242 7 6. A lubricant composition comprising an n-butyll ReferencesCited in thev file of this patent methyl polypropylene glycol dietherhaving a molecular UNITED STATES PATENTS weight of from about 400 to 800and from about onef l lth t about four-fold, in terms of the volume ofsaid 3: 1:5 eta1 2 ether of hexan'ethyl'l'butoxwdlsfloxane 5 215433735Stewart Feb: 2.7: 1951 2,643,263 Morgan June 23, 1953

1. A LUBRICANT COMPOSITION COMPRISING A DIALKYL POLY1,2-PROPYLENE GLYCOLDIETHER HAVING A MOLECULAR WEIGHT OF FROM ABOUT 400 TO 800 AND WHEREINTHE ALKYL END GROUPS CONTAIN FROM 1 TO 8 CARBON ATOMS, TOGETHER WITH ANAMOUNT OF FROM ABOUT ONE-FOURTH TO ABOUT FOUR-FOLD, IN TERMS OF THEVOLUME OF SAID ETHER, OF A MEMBER OF THE GROUP CONSISTING OF TETRAALKYLSILICATE AND HEXAALKOXY DISILOXANE WHEREIN SAID ALKYL GROUPS CONTAINFROM 5 TO 8 CARBON ATOMS EACH AND HAVE A BRANCHED-CHAIN STRUCTURE.